To produce a contact lens, a predetermined amount of flowable starting material is introduced into the female mold half. The mold is then closed by applying the male mold half. The subsequent polymerization or crosslinking of the starting material is effected by irradiation with UV light, by thermal action, or by another, non-thermal method, wherein the starting material in the mold cavity is fully cured.
In general, two types of mold systems are used to produce ophthalmic lenses such as contact lenses. The first involves the use of plastic molds produced by injection molding. The materials currently used to make the plastic molds include polypropylene, polymethylmethacylate, polyacrylonitirile, ethylene vinyl alcohol copolymer, and polyvinylidene chloride. These materials have limited chemical resistance. The starting materials used to produce the lenses can be particularly harsh and damage the surface of the mold. For example, polymethylmethacylate (PMMA) has poor chemical resistance and cannot withstand the aggressive solvents used in silicon hydrogel (SiHy) formulations typically used in the formation of contact lenses. Damage of the mold surface ultimately compromises the optical quality of the lens produced from the damaged mold. Thus, the plastic molds are generally not reusable, which presents significant economic disadvantages when manufacturing the lenses.
The second approach involves the use of glass or quartz molds that have excellent UV transmission and glass absorbing properties. Although this is a viable approach for the production of contact lenses, there are limitations. Both quartz (male mold half) and glass (female mold half) are manufactured by casting, which is very expensive and requires long lead times. Therefore, the use of glass and quartz molds is extremely cost prohibitive and time consuming.
It would be desirable to have plastic molds that are chemically resistant to formulations typically used in the manufacturing of contact lenses. Thus, the molds would be reusable and not have to be discarded after immediate use. In addition to being chemically resistant to certain reagents and starting materials, the material used to produce the mold should be readily machineable in order to produce mold surfaces with optical quality. It is also desirable that the mold material be dimensionally stable. In the case of UV curing, it is also desirable that the mold effectively absorbs UV light yet reflects and transmits little to no UV energy. Finally, it would be desirable that molds be relatively inexpensive to manufacture compared to molds made from quartz or glass. Described herein are devices that address these needs.